Cut steak into 5 cm strips; mix cornstarch and soy sauce and set aside. Heat chicken stock and set aside. Heat oil in heavy skillet or wok until very hot. Add garlic and cook for 2-3 minutes. Add beef and saute quickly, keeping it moving, just until it loses color, about 30 seconds. Add onion, salt and pepper to taste, stirring constantly for another half minute or so. Add chicken broth, bring quickly to the boil, then add cauliflower pieces, a few at a time. Cook 3 minutes, then add snow peas, stirring constantly, for another few minutes. After 7 minutes maximum, cauliflower should be tender and pea pods a bright green. Add soy sauce mixture, mix thoroughly, and stir until thickened. Turn into heavy serving dish and serve immediately.